Address CodeRabbit findings:
- Use safe cast (as?) with early return for the widget_frame lookup.
- Add contentDescription to modern list rows (theme name) and classic
  grid swatches (Color theme %d) for screen-reader support.

A full-fledged M3 dark-only theme on a true black (#000000) canvas:
green-primary action accent (GitHub style) with a bright blue secondary
for links/selection and high-contrast near-white text.

- Theme.DARK_HIGH_CONTRAST (id 25) mapped to new Theme.SagerNet.
  DarkHighContrast styles (day declares the full dark canvas so it never
  flashes light; night repeats it as the active forced-night path).
- Full M3 role overrides: surface/background/containers, surfaceVariant,
  outline/outlineVariant, secondary/tertiary, plus status semantics
  (green/red/yellow) and route/proxy blue.
- Generalize the dark-only night-mode handling: selecting any theme in
  Theme.DARK_ONLY_THEMES (Dracula, Dark High Contrast) forces night mode
  on and restores the prior setting on exit. Storage key kept for compat.
- Surfaced by name in the modern picker list (green preview swatch);
  excluded from the classic grid.
- Picker select() now follows the standard Preference contract
  (notify-then-persist) so the fragment sees the true previous theme.

Refine the OLED theme to match the intended high-contrast design and fix
two issues seen on-device:

- App bar / bottom status bar / status & nav bars now use the black
  surface instead of the green primary, via a new themable
  appBarBackgroundColor attr (defaults to colorPrimary, so all other
  themes are unchanged) wired into the shared appbar/toolbar/tab layouts.
  This reserves green for actions/selection and lets the blue/green/red
  status text read against black chrome (previously the cyan/blue detail
  text was washed out on the green bar).
- Fix the connect FAB airplane vanishing when connected: the green
  connected-icon tint was invisible on the green FAB. Add a dedicated
  fabConnectedColor attr (defaults to statusConnectedColor for back-compat)
  and set it to the dark on-primary color for Dark High Contrast so the
  icon stays visible, matching the stopped state.
- Black DHC bottom-bar style, dark ActionBar overlay, green tab
  selection/indicator on the OLED canvas.

Verified on Android across stopped/connected states.

…olor

- Correct Catppuccin Mocha palette to official values: surface = mantle
  (#181825), surfaceVariant = surface0 (#313244), and primary_dark to a
  real palette color (sapphire #74C7EC) instead of a custom mauve tint.
- Add the missing fabConnectedColor to the Dark High Contrast dialog
  styles (day + night) for consistency with the app variants and the
  other modern dialog themes.

(CodeRabbit's 'missing theme styles' findings were false positives \u2014 all
12 styles exist and were verified building and on-device.)

Give the modern themes' Widget.SagerNet.BottomAppBar.* variants an
explicit parent=Widget.SagerNet.BottomAppBar so they keep the shared
cradle/alignment/elevation config and only override backgroundTint,
rather than relying on implicit dotted-name inheritance.

Replace the last non-M3 themed widgets so the app is fully Material 3:
- SwitchCompat -> MaterialSwitch in layout_route_item and layout_apps_item.
- CheckBox -> MaterialCheckBox in layout_backup and layout_import (6 total).
- androidx.appcompat.widget.Toolbar -> MaterialToolbar in webdav settings.

All are API-compatible subclasses, so ViewBinding/findViewById and the
existing isChecked/listener calls are unchanged. Only AppCompatImageView
remains, which is the idiomatic M3 image view (not an M2 themed widget).

Verified on Android: route/apps MaterialSwitch toggles render M3 (green
on Dark High Contrast), no crashes.

- Theme picker: Dark High Contrast preview swatch is now a black circle
  with a white circumference ring (via ThemeInfo.ringColor + a
  GradientDrawable oval) so it reads as 'OLED black', not 'a green theme'.
  Other modern themes keep their solid accent dot.
- Profile + route lists: increase bottom padding to 96dp (with
  clipToPadding=false) so the last card clears the docked FAB and the
  bottom stats bar instead of being hidden behind them when scrolled to
  the bottom.

Verified on Android (DHC swatch ring; last card clears FAB at scroll end).

96dp wasn't enough: when connected, the pinned stats bar (~115dp) plus
the FAB cradle overhang (~40dp) overlapped the last card. Measured the
FAB top sitting ~431px above the screen bottom on the test device, so
bump the profile + route list bottom padding to 150dp (with
clipToPadding=false) so the last card always clears the FAB and stats
bar in both connected and disconnected states.

Verified on Android: last card fully visible above the FAB at scroll end.

- Add a RecyclerView scroll listener on the profile list: hide the docked
  FAB on downward scroll, show it on upward scroll or when the list
  settles (idle). Only acts in stable Stopped/Connected states so it
  doesn't fight the FAB's connect/disconnect animation.
- Bump profile + route list bottom padding to 168dp (FAB occupies ~157dp
  at 440dpi) so the last card always rests above the docked FAB and the
  pinned stats bar, in both connected and disconnected states.

Verified on Android (Dracula-M3, connected): last card clears the FAB at
the scroll extent; FAB tucks away while scrolling.